1. Technical Field
An embodiment of the present disclosure relates to an optical fiber temperature distribution measuring device using an optical fiber as a sensor.
2. Description of the Related Art
Optical fiber temperature distribution measuring devices that are described in JP-A-5-264370 are a type of distributed measuring devices using an optical fiber as a sensor. The optical fiber temperature distribution measuring device is configured to measure a temperature distribution along the optical fiber. This technique utilizes backscattered light occurring inside an optical fiber. Note that an optical fiber temperature distribution measuring device is also referred to as a DTS (Distributed Temperature Sensor) as necessary in the description below.
Types of backscattered light include Rayleigh scattered light, Brillouin scattered light, Raman scattered light, and the like. Temperature measurements utilize backward Raman scattered light, which has a high temperature dependence. A temperature measurement is performed through wavelength separation of the backward Raman scattered light. Backward Raman scattered light includes anti-Stokes light AS whose wavelength is shorter than that of incident light, and Stokes light ST whose wavelength is longer than that of incident light.
An optical fiber temperature distribution measuring device measures the intensity Ias of anti-Stokes light and the intensity Ist of Stokes light to calculate the temperature based on the intensity ratio therebetween, and further produces and displays the temperature distribution along the optical fiber. Optical fiber temperature distribution measuring devices have been used in fields such as temperature control in plant facilities, disaster prevention-related investigations and researches, air-conditioning for power plants and large buildings, and the like.
JP-A-2000-329646 proposes a technique relating to an OTDR (Optical Time Domain Reflectometry) measurement used in failure point search and loss distribution measurement of an optical fiber transmission path. According to the technique of this document, the OTDR distribution is corrected by using an expression (F−F*ε+F*ε*ε− . . . ), where ε is the time function of the inter-pulse portion of the transmission waveform, F is the time function of the OTDR distribution actually measured, and * is a symbol representing a convolution calculation.